To evaluate a degree of damage or injury of a road, the currant state of a road surface is represented using three factors, one of them being descent of the road caused by wheels, other one being ruggedness appearing in longitudinal and transverse directions and another one being crack developed thereon. To automate measurements for these factors which have been heretofore carried out by visual recognition, there have been made various proposals.
A conventional typical measuring system utilizing these automatic techniques is classified into two types, one of them being a slit camera system (as disclosed in an official gazette of Japanese Published Patent NO. 281915/1986) and the other one being a laser light receiving system (as disclosed in specifications of Japanese Patent Application NO. 229563/1983 and Japanese Patent Application NO. 233923/1984). According to the proposed conventional measuring systems, an image taking camera, a laser oscillator, a light receiver and other associated components are mounted on a vehicle and this vehicle intended to carry out measurements is caused to move on a road so as to allow image data representative of the road surface to be obtained by automatic measurements. Specifically, image data representative of the road surface derived from measurements for the latter are recorded in a data recorder such as a video tape recorder (VTR) or the like means and the recorded data are later analyzed to evaluate the road surface.
When the recorded data are analyzed, evaluation has been hitherto carried out by a conversation between an operator and a monitor display image surface. For example, in the laser system, a tape in which image data representative of the road surface is processed to indicate them on the monitor display via a reproducer. Then, a lattice-shaped mesh is placed on the display image surface so as to allow the latter to be divided into a plurality of square regions. The operator makes a visual determination as to whether crack is existent or not in the respective divided regions and results derived from the determination are noted on a recording paper in the form of a section paper using marks such as .largecircle., X or the like. Finally, evaluation results such as a crack occurrence rate ( =the number of meshes where crack is existent/the total number of meshes) or the like are calculated with reference to the recording paper.
As is apparent from the above description, according to the conventional systems, data representative of crack included in the image data on the road surface are analyzed by allowing an operator to make a visual determination while watching the monitor display image surface. Consequently, there arise problems that data are processed at a slow speed and an incorrect determination is made due to visual recognition.
The present invention has been made with the foregoing background in mind and its object resides in providing a method of processing image data representative of crack which assures that the image data are processed at a high speed with increased accuracy by fully automating a processing of analyzing the image data with the use of a computor.